Method of reduction by attrition



y 1950 o. C. GRUENDER 2,509,919

METHOD OF REDUCTION BY ATTRITION Filed Aug. 4, 1947 -s Sheets-Sheet 1Jlfarneys May 30, 1950 o, c, R R 2,509,919

METHOD OF REDUCTION BY ATTRITION Filed Aug. 4, 1947 3 Shets-Sheet 3172067? zar Uscar C. Qrzzewde'r 5y M/Mm Patented May 30, 1950 METHOD OFREDUCTION BY ATTRITION Oscar C. Gruender, Milwaukee, Wis., assignor toNordberg Manufacturing Company, Milwaukee,- Wis., a corporation ofWisconsin Application August 4, 1947, Serial No. 766,043

1 Claim.

My invention relates to an improved reduction or comminuting method.

One purpose is to provide a comminuting method in which fine reductionis obtained without the use of a metal grinding medium such as the ballsused in ball mills.

Another purpose is to provide a comminuting method in which some of theparticles ground perform the function of the balls normally used in aball mill.

Another purpose is to provide a reduction method in which a rapidreduction to great fineness is obtained in a mechanism of substantiallyless weight and less cost than a mechanism, such as a tube or ball mill,heretofore used in fine grinding.

Another purpose is to provide a reduction method in which an economicalreduction to great fineness is obtained in a mechanism requiringsubstantially less power than a mechanism, such as a tube or ball mill,commonly used in fine grinding.

Another purpose is to provide a, reduction method in which an economicalreduction to great fineness is obtained in a mechanism producingsubstantially less objectionable fines and slimming than a mechanism,such as a tube or ball mill, commonly used in fine grinding.

Another purpose is to provide a reduction method in a mechanism in whichthe oonsumption of steel will be substantially less than in a mechanism,such as a tube or ball mill, commonly used in fine grinding.

Other purposes will appear from time to time in the course of thespecification and claim.

I illustrate my invention more or less diagrammatically in theaccompanying drawings wherein:

Fig. 1 is a vertical, axial section through a mechanism I may employ;

Fig. 2 is a diagrammatic showing illustrating the relation of thematerial ground to the attrition members at successive nips; and

Fig. 3 is a diagram illustrating the particles in the attrition zonewhen the attrition members are in position of closest approach.

Referring to the drawings, Fig. 1 illustrates a structure which may beemployed to carry out my method and which has some resemblance tocurrently manufactured gyratory crushers but differs basically from themin operation. Since the particular structure involved does not of itselfform part of the reduction method, I have not fully shown it. Thestructure is more completely shown in my co-pending application SerialNo.

766,044 filed on the same date as the present application.

Referring to Fig. 1, I generally indicates a circumferential main framemounted on any suitable base not herein shown. 2 illustrates a centralpost which will be understood to be mounted on the main frame structure.3 indicates an upward projection from the main frame structure. 4 is aneccentrically apertured sleeve which rotates about the fixed post 2 andmay be rotated by any suitable means not herein shown. It has an upwardextension or sleeve 5 which carries a feed plate support 6, to which issecured the centrifugal feed plate So. It will be understood that whenthe eccentric sleeve 4 is rotated the feed plate 6a is also rotatedthereby.

Surrounding the exterior of the eccen'trically apertured sleeve 4 is ahead I which is provided with a downwardly convex spherical bearingsurface .8 received by an appropriately formed bearing ring 9 upon theframe portion 3. III, II are any suitable sealing members and I2 is atrough in which water may be received. The result is an adequate sealingstructure which, however, forms no part of the present invention andwill not be further discussed.

I4 is a bowl support ring resting on the abutment ring Me which, inturn, rests on themain frame I. I5 indicates the bowl which isadjustable upon the ring I 4 as by the interpenetrating threads IE. ITis any suitable conic hopper mounted on the bowl l5 and adapted toreceive the feed centrifugally delivered by the rotating plate 6a. I8 isany suitable feed spout adapted to deliver the material to the top ofthe feed plate Ga.

I illustrate two opposed and replaceable attrition liners or dies. 20 isan upper liner assembly secured to the bowl l5, as by the securingstructure 2|, the details of which do not form part of the presentinvention. 22 is a lower die or attrition member which is held inposition by the combined hopper and thrust member 23, which, in turn, isheld by the locking ring 24 secured to the upward extension 25 of thehead 1. Whereas the various details do not of themselves form part ofthe present invention, it will be understood that the result of therotation of the eccentric sleeve 4 will be a simultaneous rotation ofthe feed plate 6a and gyration of the head I. With the upper attritionmember 20 normally fixed, the result will be a movement of the lowermember or die 22 toward and away from the fixed member 20, as indicateddiagrammatically in Fig. 2. Appropriate sealing means entry st into themechanism rotary movement of the plate Ga and gyratory moveme of thehead 3. Thus the ring 25 has upward scaling connection Qiia which whetrates into an appropriate channel 2% in the bottom oithemembe': r

in considering. the nature (if my method, I employ an initial feed whichmay vary widely from mine to mine. It is certainly important, and, ingeneral, necessary that there he a. pro.- portion of oversize particleswhich will perform functions of the metal balls or pebbles or theconventional ball mill. in addition to this function, the coarseparticles tend to maintain a satisfactory volume of voids and preventpacking. As an example of a useful range of size, I may employ a feedhaving about coarse particles and 80% fine particles. The coarseparticles may be plus V8" to minus The fine particles may be minus andplus 65 mesh. While I do not wish to be limited to a specific range, theone above described is practical.

In carrying out my method, the coarser particles should be generallyuniformly distributed throughout the mass, to prevent segregation andunequal grinding. Y

My method can be carried out e'ther dry or wet, and with variousproportions of water. For example, I may have water to the extent of 40%or,50% of the whole, throughout a substantial range. However, I cannotuse so large a proportion of water as to cause a. rapid cascading orflushing of the particles through the attrition zone.

With reference to Figs. 1 and 3, and with a feed conforming to thegeneral characteristics above discussed, the rotation of the fee-:1plate So will deliver the particles violently outwardly against thehopper l1. fine and coarse particles are delivered downwardly throughthe spout 18 in segregated condition, the rotation of the plate 6a iseffective to provide adequate mixture, and the particles, with thecoarse elements satisfactorily scattered through the mass, will movegravitally down the slope of the hopper ll. As shown in Fig. 3, thecrushing cavity normally will be bridged as at A. Fig. 3 shows the upperand lower attrition members 20 and 22 at their closest approach. Buteven when they are at their greatest recession, normally there willstill be a bridging mass at A, which serves as a restriction and controlfor the entry of the particles to the grinding zone proper at B, betweenthe opposed members 20 and 22.

At each recession of the member 22 downwardly away from the normallyfixed member 20 there will be an entry, from the zone A, of particlesinto the opening of the zone B. As a matter of fact, the upper, innerend of the grinding cavity B normally will be substantiall entirelyfilled with a mixed mass of fine and coarse particles. As a result, whenthe attrition excursion begins, the material or mass caught by the firstnip is directly compressed. However, there are sufficient voids in themass to prevent its reduction to an incompressible packed mass. Thelength of stroke and the timing of the movement of the head are suchthat, after the initial nip, the head, with the lower attrition member22, is withdrawn faster than the previously crushed mass is acceleratedby gravty. Thus, the member 22 recedes downwardly away from the fallingmass. Significantly, the timing and excursion In the event that the aresuch member 22 has reached its lowe t position is again rapidly movingupy tower the member 2i) before it receives the The result is ashattering or oi the causing the particles to assume a new position inthe mass, with the stroke terminating in a. compression nip.

At no stage is there a single layer crushing or grinding effect. is tosay, there are no particles of sumcient size to be directly grippedbetween the members 20 and 22. On the contrary, the mass is squeezed ornipped between the opposed surfaces the members 20 and 22, with aresultant grinding of particle on particle, and a reduction by attritionof a multi-layered mac I After the iirst compremlng nip with a fullcavity, there is a. sequence, at each nip, of a free gravital fallterminated by an impact against the falling mass. However, since thecompressing or impacting nip is delivered perpendicularly to thegrinding surfaces, there is a minimum of abrasive or glancing or cuttingaction on the metal surfaces of the opposed attrition members.

It will be noted that the angle of the upper surface of the lower member22 is less than the angle of repose of the material undergoingreduction. Thus, it the member 22 were at rest, the material deliveredto its upper surface would not of itself slide downwardly through theattrition zone. The propulsion of the material through the attritionzone, or zone of treatment B, is generally positive, in response to thecarrying movement of the head. There is only an incidental or slightsliding movement of the particles outwardly through the discharge zone.This propulsiv action is well illustrated in Fig. 2. The

form 50 indicates the compressed mass in the polsaition in which it isplaced by the nip of the mem- As the member 22 recedes downwardly, themass 50 may theoretically be considered to be falling to the position5011. When it is again picked up by the lower member 22 it is movedoutwardly, and, owing to the slope of th member 22, is carried or liftedto the advanced position 50b. The space left at the upper or inner endis filled by particles flowing in from the space A. The particles at theend of the form 50b fall downwardly out of or away from the zone oftreatment. It will thus b evident that with the proportion Of the parts20 and 22, as shown, and with the center of gyration located at X inFig. 1, the mass undergoing treatment will be moved progressivelyoutwardly through the zone B in a series of relatively short steps, andthat the ratio of reduction of the mass during the first step or initialcompression nip will be considerably greater than the ratio of reductionof th mass during the subsequent steps or compression nips.

It is characteristic of my method that the particles are maintained in amulti-layer condition, with the coarse particles scattered reasonablyuniformly through the mass. passes through the zone of treatment, thnumber and size of the coarser particles are progressively reduced, asindicated diagrammatically in Fig. 3. However, I find it important tooperate my method in closed circuit. The product of each stage of theattrition method is subjected to separation by size, by means not hereinshown. The properly reduced material is removed from the circuit and theoversize, with additional feed, is returned to the closed circuit, toform part of the feed of the ensuing passage. In practice, as in the Asthe material conventional ball mill, the circulating load may be as lowas 300% and as high as 600% or more, depending upon the nature of thefeed and of the mat-"rial materials being fed.

It will be observed that I provide an attrition zone that is more orless continuously restricted in depth, from the feed end to thedischarge end, as shown in Fig. 3; and that the attrition members 22 and20 are set relatively far apart. In other words, close setting of thattrition mem hers is not required to produce a product which containsa, large percentag of extremely fine sizes.

It will be realized that-whereas I have shown an adequate mechanism forcarrying out my method, the method maybe carried out by differentmechanisms and is not a mere function of th particular mechanism shown.

I illustrate a method, and a structure for carrying it out, in which anattrition zone is proimportant that the attrition members, at theirclosest approach, are still separated by a distance suflicient to admita layer of small particles of substantial thickness. .These particlesare arranged in a layer of a depth many times the diameter of thelargest particles passing through the attrition zone, at all positionsof the movable member.

In the normal use of the structure illustrated in the drawings it willbe understood that the lower attrition member 22 need not have anysubstantial rotation. Whereas the hub or sleeve I is free to rotateabout the exterior bearing surface of the eccentric 4, no means forrotating it are provided, and it rotates merely in response tofrictional contact with the material undergoing crushing, and at a rateinsufficient to have any perceptible effect on the crushing method.However, I find it advantageous to provide a positi-ve mixing andfeeding of the particles to the attrition zone. I therefore rotate thefeed plate 6a in response to rotation of the eccentric 4. In theparticular structure herein shown, I illustrate the plate So as directlydriven by the upward extension 5 of the eccentric 4. The rate ofrotation of the eccentric is, in practice, suflicient to impart a verysubstantial centrifugal outward delivery of the particles, as isdiagrammatically indicated in Figure 1. Th particles, in mixed sizes,are de-- livered downwardly through the spout t8, and, in response tothe mixing and centrifugal delivering movement of the plate 6a, theparticles are fed in a relatively thin stream or layer, under conditionsand ate. rate of speed adapted to maintain a substantially uniformmixture of coarse particles throughout the mass. The outward movement ofthe fed particles is terminated by conof repose of the materialundergoing reduction,

while keeping the attrition members at all times substantially apart;providing a. feed in which a proportion of coarse particles is mixed ina mass of fine particles; centrifugally mixing and delivering the feedin a relatively thin and generally horizontal stream at a. suflicientrate of speed to maintain a substantiall uniform mixtur of coarseparticles throughout the mass, as the mass enters the attrition zone;normally delivering sufficient feed into the receiving aperture of theattrition zone to maintain a bridge of material between the opposedattrition members at all positions of the attrition members; initiallysubjecting the entering mass to compression between the opposedattrition members; withdrawing the lower attrition member downwardlyfrom the upper at a rate and through an excursion suflicient to withdrawit, after each compression, faster than the acceleration under gravityof the previously compressed material; returning the lower attritionmember upwardly toward the falling mass and catching the falling massthereon when the lower member is moving upwardly with suflicientrapidity to impact and scatter the falling mass; maintaining thesequence of free fall of the mass and of impact against the'mass, untilthe particles undergoing attrition escape from the attrition zone, whileemploying the lower member as the means for conveying the mass throughthe attrition zone, with the particles arranged in a layer of a depthmany times the diameter of the largest particles passing through the!attrition zone, at all positions of the movable attrition member.

OSCAR C. GRU'ENDER.

REFERENCES CITED The following references are of record in the file of-this patent:

UNITED STATES PATENTS Number Name Date 933,669 Rusager Sept. 7, 19091,057,773 Pratt Apr. 1, 1913 1,226,275 Symons May 15, 1917 2,254,425Fahrenwald .Sept. 2, 1941 FOREIGN PATENTS Number Country Date 656,857Germany b. 17, 1938

